At the Doctor's trial, the Valeyard presents the Doctor and Peri's most
recent adventure. The dying words of a Thordon warlord send the pair to
Thoros-Beta, home of the Mentors -- including their old foe, Sil. The
Mentor leader, Kiv, has had his intelligence enhanced by the human
geneticist Crozier, but now his brain is outgrowing his skull. Crozier
sets his eyes on Peri as the new host for Kiv's brain. But when the Doctor
appears to turn evil under the effects of one of Crozier's devices, it is
left to the berserk warlord King Yrcanos to save his companion.

Production

The villainous Sil, created by Philip Martin for his Season Twenty-Two
story Vengeance On Varos, had proved highly
popular with Doctor Who producer John Nathan-Turner and script
editor Eric Saward. Martin was quickly asked to bring the character back
for a second encounter with the Doctor. Originally, this would have
occurred in a serial entitled “Mission To Magnus”, which
paired Sil with the Ice Warriors and was likely intended to be the
fourth story of Season Twenty-Three. However, this adventure became one of
the many casualties of the BBC's decision to delay and shorten that
season, leading to the development of a new set of scripts linked by the
common thread of the Doctor being placed on trial by the Time Lords.

Martin was part of the team of writers assembled for the new Season
Twenty-Three, alongside Robert Holmes, David Halliwell and Jack Trevor
Story. The season was envisaged as following the pattern of the 1846
Charles Dickens novel A Christmas Carol, with evidence at the trial
given in the form of the Doctor's past, present and future adventures.
Martin was tasked with devising the “present” chapter --
that is, the Doctor's most recent escapades prior to being summoned to
face the Time Lord courtroom. Once again, he was asked to incorporate
Sil into his storyline. But a more dire requirement for Martin's serial
was that it should culminate in the death of Peri, whom the production
team had decided to replace with a new companion, Melanie Bush, partway
through the year. Nicola Bryant, meanwhile, was beginning to worry that
her acting career might suffer from a prolonged association with a
single role, and so she was agreeable when Nathan-Turner informed her of
this turn of events.

Philip Martin was instructed that his scripts should
culminate in the death of Peri

Since writing Vengeance On Varos, Martin had
joined BBC Radio as a drama producer; consequently, staff clearance was
requested for Martin's Doctor Who scripts on September 13th,
1985. The title “The Planet Of Sil” was originally applied
to Martin's story, which soon became known as “Mindwarp” and
designated Serial 7B. Ron Jones was engaged as director; he had helmed
Vengeance On Varos and likely would have
served in the same capacity on “Mission To Magnus”. Sadly,
these episodes would be amongst Jones' final television work. After
spending some time directing for German broadcasters, his career was
prematurely curtailed by a long illness. Jones died on July 9th,
1993.

As “Mindwarp” neared production, Nathan-Turner decided that
the entirety of Season Twenty-Three should be broadcast as a single,
fourteen-episode serial. Consequently, Martin's story would become parts
five to eight of The Trial Of A Time Lord. Amongst the cast
assembled by Jones was Brian Blessed, an acclaimed Shakespearean actor who
had risen to prominence on television in the police drama Z Cars.
In August 1983, Blessed had been widely -- if erroneously -- reported by
the British press as the man who would succeed Peter Davison as the star
of Doctor Who. Nabil Shaban had also agreed to reprise the role of
Sil.

Recording for the second segment of The Trial Of A Time Lord began
under a cloud. The rapport between Nathan-Turner and Saward had been
deteriorating for some time, as the script editor increasingly found
himself disagreeing with his producer's decisions. On April 13th, Saward
resigned his post but agreed to complete his friend Robert Holmes'
script for the season's concluding episode, since the writer was now too
ill to work on it himself. Sadly, Holmes passed away on May 24th,
placing a further strain on the relationship between Nathan-Turner and
Saward. The situation had also impacted rehearsals on Martin's
adventure, with Colin Baker finding that no one could explain to him
whether the Doctor's aberrant behaviour was meant to be a genuine
reflection of the effects of Crozier's machine, a ruse, or evidence of
tampering with the Matrix record.

No one could explain to Colin Baker whether the Doctor's
behaviour was genuine, a ruse, or evidence of tampering with the
Matrix

Parts five to eight of The Trial Of A Time Lord were largely
studio-bound, taped in two three-day sessions. The first block began on
Tuesday, May 27th in BBC Television Centre Studio 1. Here, an uncredited
Deep Roy wore a repainted Terileptil mask (from Season Nineteen's The Visitation) as the Possican delegate. The
initial two days concentrated on scenes in Crozier's laboratory and the
corridors, including Peri's death scene (for which Bryant wore a bald
skullcap). Unfortunately, painstaking lighting changes in the corridors
provoked a labour dispute, and as a result the work proceeded slowly.
Consequently, the completion of material in Kiv's chamber and profit
room on the 29th represented significantly less than Jones had planned
to accomplish to that point, despite permission being granted for a
fifteen-minute overrun.

Happily, the second studio block, which started on Wednesday, June 11th
in TC6, was a smoother affair. Nonetheless, there was another flare-up
of the industrial strife which had plagued the first session, when the
lighting crew objected to the lowering of two lighting rigs for use as
the circular entrances to the Alphan Induction Centre. A compromise was
eventually reached whereby the actual lights on these rigs would not be
turned on. Tunnel and corridor scenes were scheduled throughout this
block. Otherwise, the first day dealt with the sets for Matrona Kani's
chamber, the cell, and the tide control room; the second with the
caverns and the problematic Induction Centre; and the third with the
Time Lord courtroom.

Production then wrapped up with location filming on June 15th and 16th
at Telscombe Cliffs near Peacehaven in East Sussex, for sequences on the
pebble beach and at the Rock of Sorrows. Unfortunately, a crewmember had
accidentally noted the times of high and low tide in reverse, which
resulted in the water being much deeper than anticipated when shooting
the scene of the Doctor and Peri arriving on Thoros-Beta. In
post-production, Jones elected to use a new digital compositor called
Harry to alter the colours in these scenes. This was in accordance with
Martin's scripts, which described Thoros-Beta as boasting purple
mountains, a bright green sky, and a pink sea.

Nicola Bryant was disappointed to learn that John
Nathan-Turner had changed his mind about Peri's death

The conclusion of work at Telscombe Cliffs marked the end of Nicola
Bryant's tenure on Doctor Who. The actress was pleased that Peri's
death represented a powerful and unusual exit for a companion.
Consequently, she was disappointed to learn that Nathan-Turner had changed
his mind about the manner of her departure, with the season's closing
episode now revealing that Peri's death was a fiction conjured by the
Valeyard. Much of Bryant's subsequent career concentrated on the theatre,
although she continued to make periodic television appearances, including
Blackadder's Christmas Carol, Holby City and Doctors.
She reprised her role as Peri for the thirtieth-anniversary special
Dimensions In Time in 1993, and on many
occasions for Big Finish Productions' range of Doctor Who audio
dramas, beginning with Whispers Of Terror in November 1999.

This was also Philip Martin's last televised Doctor Who story.
Although much of his later work would be in radio, he continued to write
occasionally for television as well, such as episodes of Star Cops,
The Bill and Doctors. He novelised both of his broadcast
Doctor Who adventures, as well as “Mission To
Magnus”, for Target Books. More recently, he contributed several
scripts to Big Finish, including an audio adaptation of “Mission
To Magnus”.